Digital data has been recorded as punched holes in a paper medium in the form of paper tape and IBM cards. The hole entries were necessarily large resulting in a very low density data format. Digital data has also been recorded on paper medium by the conventional printing of ink pigments. The pigment entries were typically black and somewhat smaller then the punched holes, producing a somewhat higher density format.
Laser beam printing on paper offers a higher density format. Current printer have an ink dot density of 300 dot per inch (dpi) with a dot diameter of about 3 mils. However peripheral dispersion of the particles of toner dust limits the closeness of adjacent entries in the data format. High density dots with toner dispersion may introduce read errors when the digital data is retrieved. In addition, the toner dots may be out of registration or irregular in shape further limiting the recording density.